Sleeping bags generally can be divided into 2 groups: down-filled sleeping bags and synthetic-fiber filled sleeping bags. It is obvious that the difference between them is mostly referring to the different insulating materials. Construction wise, the down and synthetic fiber sleeping bags are made differently, but they do share some similarities.
Synthetic Fiber Construction
The synthetic fiber used in sleeping bags is typically made up of polyester fiber filaments. The filaments are then processed (mixing and heating) in the form of a padding. The thickness of the padding makes synthetic fiber a good thermal protection material to trap air. The air is trapped within the dense confines of the fiber network. Given that the synthetic fiber is not a good heat conductor, the heat (warmth) will stay within the system longer. The combination of the synthetic fibers and the trapped air provides a good insulation system, especially for sleeping bags. There are 2 different types of construction utilized in synthetic sleeping bags: Layer construction and Shingle construction.
Layer construction as depicted in FIG. 1, is just a simple padding of synthetic fiber on other material. This is the simplest way to construct a sleeping bag.
As depicted in FIG. 1 there are 2 layers of synthetic fiber in each of the top and bottom half. In both the top and bottom halves, one layer is stitched to the shell fabric and the other layer is stitched to the lining fabric. This construction is typically referred to as 2-layer quilt construction since there are 2 layers of synthetic fibers covering around the body.
Shingle construction consists of a series of parallel fixed synthetic fibers which overlap as depicted in FIG. 2. Because of the overlapping, sleeping bags made with shingle construction general provide better (higher) loft. FIG. 2 depicts a 2-layer shingle construction. The way to see it is to look at the xe2x80x9cCross section linexe2x80x9d. As you move the line forward and backward long the length of the bag, at any given point, you will see 2 layers of padding. This may not be as obvious as the 2 layers in layer quilt construction, but it does give the same result in which you will have 2 layers of insulation covering around user""s body.
Down Filled Construction
The thermal protection of down is very well established, especially in the apparel business. Due to its exceptional thermal protection and its lightweight, down is also very commonly used in sleeping bags. Other materials characterized by low thermal transfer rates and relatively light weight are also used in lieu of down. FIGS. 3 and 4 depict the two most common constructions concerning down sleeping bags.
The key to the down sleeping bag construction is to fill a series of compartment space with down. FIG. 3 depicts a vertical box construction. Scrim netting (polytricot) is typically used to form compartments. The scrim netting is very similar to synthetic fibers but it is typically significantly lighter and denser in its construction. The netting is usually 100% polyester but other materials can be used. This netting offers no insulating value and its function is nothing more than providing lightweight medium to contain the down in each of the compartments.
The slant box construction depicted in FIG. 4, is very similar to synthetic fiber shingle construction. The differences being the scrim netting in lieu of synthetic fibers and the addition of down in the compartments formed.
This invention consists of a new method for construction of sleeping bags and the applications in which improved insulation properties are desired. This invention provides a method to improve insulation characteristics by adding additional compartments to show the thermal transfer rate while also increasing loft. This invention can be applied in both the synthetic fiber construction as well as the down filled construction.